Production and purification of vinyl chloride

ABSTRACT

This invention relates to a novel process for the production of vinyl chloride by thermal decomposition of dichloroethane and high pressure distillation for purification of the product mixture to recover vinyl chloride. The present invention utilizes two combinations of dual distillation zones which co-act to cancel the effects of &#39;&#39;&#39;&#39;sloppy&#39;&#39;&#39;&#39; cut distillations in each zone to achieve substantially pure product streams and a substantially pure recycle stream while still effecting a considerable refrigeration saving.

United States Patent Wall, Jr. Feb. 18, 1975 [54] PRODUCTION AND PURIFICATION OF 2,715,606 8/1955 Grote 203/21 VINYL OR 2,900,312 8/1958 Gilmore 202/160 3,238,735 3/1966 Siewert 62/28 Inventor: Henry a J Baton Rouge, 3,357,901 12/1967 Otsuka er al.... 203/78 La. 3,365,375 [/1968 Nixon 203/82 3,404,175 10/1968 Mercier 203/84 X [73] Asslgnee- Elhy' cmporamn, Rlchmond, 3,484,493 12/1969 Krekeler et al. 260/656 R 22 il Man 11 1974 3,801,660 4/1974 Coppens 260/656 R pp N95 4499769 Primary Examiner-A, Louis Monacell Related Application Data Assistant ExaminerDavid Edwards [60] Continuation-in-part of Ser. No. 95,972, Dec. 7, gf g g g g g'l" Johnson; John 1970, abandoned, which is a division of Ser. No. 1e ert gar ple 632,002, April 19, 1967, abandoned.

[57] ABSTRACT [52] US. Cl 203/81, 203/87, 203/98, This invention relates to a novel process for the pro- 260/656 R, 202/162 duction of vinyl chloride by thermal decomposition of [51] Int. Cl B0ld 3/14, 801d 3/32 dichloroethane and high pressure distillation for puri- [58] Field of Search 203/7187, fication of the product mixture to recover vinyl chlo- 203/21-23, 27, 39, D16. 9, 99, 98, 40; ride. The present invention utilizes two combinations 202/153-162, 185; 260/656 R; 62/28, 29, 31; of dual distillation zones which co-act to cancel the 261/114, 157, 153 effects of sloppy cut distillations in each zone to achieve substantially pure product streams and a sub- [56] References Cited stantially pure recycle stream while still effecting a UNITED STATES PATENTS considerable refrigeration saving.

2,609,334 9/1952 Pyle et a1. 203/40 9 Claims, 3 Drawing Figures I :IIS 8 p 5 PRODUCTION AND PURIFICATION OF VINYL CHLORIDE CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of pending application, Ser. No. 95,972 which was filed Dec. 7, i970, and now abandoned which in turn is a divisional application of Ser. No. 632,002 filed Apr. 19, I967, which is now abandoned.

BACKGROUND OF THE INVENTION It is known that vinyl chloride can be produced by thermally decomposing either l,2-dichloroethane or 1,1-dichloroethane or both in a cracking furnace at temperatures of about 400C and higher. This decomposition involves the splitting off of hydrogen chloride from the dichloroethane molecule, to produce a resulting mixture of reactants and cracking products which presents a difficult separation problem. One difficulty encountered in commercial applications of the process is the expense of costly refrigeration systems and refrigerants necessary for the purification of the product stream from the cracking furnace.

It is an object of this invention to provide a process wherein the requirement for refrigeration in the product distillation columns is greatly minimized.

Another object of this invention is to provide a process for the commercial production of vinyl chloride in a more simple and economical manner.

SUMMARY OF THE INVENTION stream containing vinyl chloride, hydrogen chloride and unreacted dichloroethane, and a liquid stream con taining substantially pure unreacted dichloroethane; passing said gaseous stream to a primary column of a secondary distillation zone, said primary column being divided into upper and lower zonules by an intermediate blocking means; further distilling said gaseous stream in said primary column while, withdrawing from the upper zonule a gaseous distillate containing substantially pure hydrogen chloride, and a liquid distillate containing hydrogen chloride, vinyl chloride and unreacted dichloroethane, withdrawing from the lower zonule a gaseous effluent containing hydrogen chloride, vinyl chloride and unreacted dichloroethane, and a liquid effluent containing substantially pure vinyl chloride and unreacted dichloroethane, and passing at least part of said liquid distillate into said lower zonule and at least part of said gaseous effluent into said upper zonule; finally distilling said liquid effluent in a secondary column of said secondary distillation zone to produce a gaseous product stream of substanially pure vinyl chloride, and a liquid mixed stream of vinyl chloride and unreacted dichloroethane; and recycling said liquid mixed stream to said primary distillation zone.

BRIEF DESCRIPTION OF THE DRAWING For a more complete understanding of the present invention, reference is made to the accompanying drawings.

FIG. I is a diagrammatic illustration of a system which may be suitably employed to conduct the process as hereinafter described.

FIGS. 2 and 3 show modifications of the detailed construction of the Hydrogen Chloride Column of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in the embodiment of FIG. I, dichloroethane (either 1,1-dichloroethane or 1,2-dichloroethane is fed by line 1 into a thermal cracking zone, e.g., a furnace, which maybe an unpacked reaction vessel supplied with heating means. The pressure of the gaseous reactants within the zone is maintained at from about atmospheric pressure to less than about I00 pounds per square inch gauge and preferably from about 25 pounds per square inch gauge to about pounds per square inch gauge. The temperature within the zone is generally maintained at from about 800 to about 900F and preferably from about 825 to about 875F.

The gaseous product stream from the thermal cracking zone is withdrawn via line 2 at a temperature of from about 825 to about 875F and quenched by a circulating liquid stream 4 from a quenching zone, e.g., knockout drum A, to reduce the temperature of stream 2 to about 250F and thereby form a gaseous phase and a liquid phase. Stream 4 is supplied by circulating a part of this liquid phase. A small part of stream 4 comprising carbon and tars may be withdrawn via stream 5 and sent to waste disposal if necessary.

The gaseous phase is withdrawn via line 3 from the quenching zone and passed to a condensation zone, e.g., condenser B. Therein the vapor stream is partially condensed to a liquid portion and a gaseous portion, which coexist as a two-phase mixture. This two-phase mixture is passed from the condenser via line 6 into a disengaging zone or a knockout drum C wherefrom the liquid portion, which is composed principally of dichloroethane, is removed via line 7. Part of the liquid portion is recycled to the quenching zone via line 8 to be reunited with the liquid phase. The remainder of stream 7 is passed via line 18 to a distillation zone, preferably though not necessarily a single column, wherein a pressure of from about 30 pounds per square inch gauge to about 60 pounds per square inch gauge is maintained. This zone is depicted in the drawing as the Dichloroethane Column.

The gaseous portion from drum C is withdrawn via line 9 at a temperature of from about 90 to about F and a pressure of from about 30 pounds per square inch gauge to about 50 pounds per square inch gauge and is compressed together with stream 10, a gaseous stream from the Dichloroethane Column, in a compression zone, e.g., compressor D, to a pressure of less than 300 pounds per square inch gauge and preferably within the range of from about pounds per square inch gauge to about 200 pounds per square inch gauge. In a typical process run, stream 11 comprises about 55 weight percent hydrogen chloride, about 43 weight percent vinyl chloride and about 2 weight percent dichloroethane. Thev temperature of the compressed stream ranges from about 315 to about 335F.

The compressed stream 11 is cooled in cooling zone E to a temperature of from about 50 to about 150F, and preferably from about 90 to about 1 10F, to form a two-phase liquid-gas stream, and this stream is trans- 3 mitted by line 12 to a further distillation zone, preferably though not necessarily comprising two columns as shown in the drawing. The first column, labelled the Hydrogen Chloride Column (hereinafter more fully described), is maintained at a pressure of from about 150 pounds per square inch gauge to about 200 pounds per square inch gauge. This column contains distillation trays or their equivalent in the form of packing. The overhead from this column, which contains substantially all of the hydrogen chloride as a substantially pure by-product, is withdrawn via line 13 at a tempera ture of from about 20 to about -lOF, and the heavy ends of the column containing primarily vinyl chloride and some unreacted dichloroethane are removed at a temperature of from about 160 to about 180F and transmitted via line 14 to a second distillation column. This column, labelled the Vinyl Chloride Column, is maintained at a pressure of from about 140 pounds per square inch gauge to about 160 pounds per square inch gauge. From this column the remaining dichloroethane is withdrawn at a temperature of from about 190 to about 210F in a bottoms stream having a substantial quantity of vinyl chloride therein. The vinyl chloride may range from about 40 weight percent to about 60 weight percent of the bottoms stream. This stream is recycled via line 15 to the first distillation zone which is depicted as the Dichloroethane Column in the draw- Substantially pure vinyl chloride is recovered from the top of the second column at a temperature of from about 90 to about 110F This stream is removed via line 16 and sent to storage. It is possible to achieve substantially pure vinyl chloride and dichloroethane by making offsetting sloppy cuts in the Vinyl Chloride and Dichloroethane Columns. Thus, while pure vinyl chloride is removed via line 16, a considerable amount of vinyl chloride is also removed via line 15 along with unreacted dichloroethane. This sloppy cut is offset in the Dichloroethane Column which separates the feed streams 15 and 18 into a stream 17 of substantially pure dichloroethane and an impure stream 10 containing a quantity of dichloroethane which is substantially returned to the Hydrogen Chloride Column and Vinyl Chloride Column. Stream 17 from the Dichloroethane Column is removed at a temperature of from about 270 to about 290F and after purification may be recycled to the thermal cracking zone.

As explained, the present invention utilizes dual distillation zones which co-act to cancel the effects of sloppy cuts in each and thus achieve substantially pure product streams and a substantially pure recycle stream while still effecting a considerable refrigeration saving. The term sloppy is a word peculiar to the art. By this term it is meant that a distillation column is operated under such conditions that one substantially pure product stream is obtained. Such a product stream may be either the overhead or bottoms of the column, but not both, since the other stream from the column is impure with some quantity of the material comprising the product stream. A sloppy cut is the opposite of a sharp cut which means that a distillation column is operated under such conditions as to obtain .a substantially pure overhead and a substantially pure bottoms. Columns utilizing sharp cuts are difficult tocontrol and require considerable refrigeration; additionally there are problems with reboiler fouling. The present invention avoids these difficulties by utilizing sloppy cuts. And, through co-acting distillation zones, the impure overhead from the first zone is transformed in the second zone into a pure overhead and impure bottoms, and the impure bottoms from the second zone is returned to the first zone to be transformed into a pure bottoms and an impure overhead. Hence, the two sloppy cuts cancel out and a pure product overhead and a pure recycle bottoms are achieved.

FIGS. 2 and 3 of the drawing show an additional aspect of the present invention wherein it is found advantageous to use offsetting sloppy cuts. That is, the Hydrogen Chloride Column employs offsetting sloppy cuts by means of dual zonules within the column. This allows the achievement of a substantially pure overhead stream of hydrogen chloride and a substantially pure bottoms stream of vinyl chloride and unreacted dichloroethane. The manner in which this is accomplished will be apparent from the following description of FIGS. 2 and 3.

Multi-component stream 100, which in the preferred embodiment is vinyl chloride, hydrogen chloride and unreacted dichloroethane, is passed to condenser 101. There stream is transformed into two-phase stream 102 and passed into settling drum, 103. From drum 103 there is passed gaseous phase 104 and liquid phase 105 to distillation column 106. As will be noted in the modification of FIG. 2, distillation column 106 is divided into zonules 107 and 108 by blind plate 109. As is common in distillation, gaseous phase 104 passes up through zonule 107 and is distilled while liquid phase 105 passes down through zonule 108 and is also distilled. A vapor stream is withdrawn from zonule 107 via line 110 and passed through a condenser 111. Pure hydrogen chloride is extracted via line 112 while some hydrogen chloride is admitted back to zonule 107 in liquid form via line 113 as reflux. A similar operation happens in zonule 108; a liquid stream is withdrawn and part of it is passed via line 114 through reboiler 115 to form gaseous stream 117. Substantially pure liquid vinyl chloride and unreacted dichloroethane are extracted via line 116, and stream 117 is readmitted to zonule 108. Meanwhile, liquid distillate is being withdrawn from zonule 107 via line 118 and readmitted to multi-component feed stream between condenser 101 and drum 103. Also, vapor effluent 119 is being withdrawn from zonule 108 and readmitted to the multicomponent stream ahead of condenser 101. Of course, stream 118 may also be admitted ahead of condenser 101, dependent upon the extent of pressure drop across condenser 101. Thus, it is possible to employ sloppy cuts in both zonules 107 and 108 since streams 118 and 119 are both impure and are remixed to be redistilled with multi-component feed stream 100. On the other hand, streams 112 and 116 are substantially pure. Hence, through use of blind plate 109 and the remixing of two impure streams from sloppy cuts with the feed stream, a pure overhead stream and a pure bottoms stream from one column are achieved with minimum operational difficulty.

The modification of FIG. 3 is similar to that shown in FIG. 2 but with the following differences. Instead of using a blind plate in the column of FIG. 3, there is employed a zone of cooling coils 120 through which is passed cooling water via lines 121. This allows a liquid distillate from zonule 107 to pass down through cooling zone 120 into zonule 108. On the other hand, gaseous effluent from zonule 108 passes up through cooling zone 120 into zonule 107. Both the aforementioned liquid distillate and gaseous effluent are impure inasmuch as the liquid distillate contains part of the hydrogen chloride extracted via line 112 and the gaseous effluent contains part of the components of the vinyl chloridedichloroethane stream extracted via line 116. Cooling zone 120 turns column 106 into two zonules whereby the top zonule produces a pure overhead and an impure bottom stream and the lower zonule produces an impure overhead and a pure bottom stream. Thus, the two impure streams are allowed to cancel each other whereby it is possible in one column to achieve both a pure overhead stream and a pure bottom stream by utilizing offsetting sloppy cuts in dual zonules. Unlike the modification shown in FIG. 2, it is not necessary to withdraw a liquid stream 118 and a gaseousstream 119 and remix these streams with the multi-component feed stream.

In order that those skilled in the art can thus appreciate the process of this invention, the following examples are given by way of description and not by way of limitation.

EXAMPLE I chlorinated compounds such as l,l,2-trichloroethane.

This stream from the furnace was at a temperature of about 850F and a pressure of about 60 psig. The stream was quenched and fed into a knockout drum. A liquid stream from the knockout drum at 225F was recirculated as a quench medium. A vapor stream from the drum at 225F and 55 psig was withdrawn and passed to a condenser, partially condensed and cooled to a temperature of 100F, and then sent to a disengaging drum wherein the stream was separated into a liquid and a gas phase. The liquid phase was composed primarily of l,2-dichloroethane; 70 weight percent of this liquid was recycled back to the knockout drum. The balance of the liquid was passed to a Dichloroethane Column which was operated at a pressure of about 50 psig. The gaseous phase, which was composed primarily of vinyl chloride and hydrogen chloride, was passed at a pressure of about 45 psig and a temperature of about lO0F along with a vapor stream from the Dichloroethane Column at a temperature of 100F into a compressor wherein the pressure was raised to about 200 psig and the temperature was raised to about 335F. This compressed stream was cooled in a heat exchanger to a temperature of about 100F and sent to a Hydrogen Chloride Column. This distillation column was equipped with standard distillation trays and a reflux condenser and was operated at a pressure of 170 psig. Substantially pure hydrogen chloride was recovered from the overhead of the column at a temperature of 1 5F; the bottoms, composed of vinyl chloride and l,2-dichloroethane at a temperature of about 170F, was fed into a Vinyl Chloride Column equipped with trays and a reflux condenser and operated at a pressure of 150 psig. Substantially pure vinyl chloride was recovered as the overhead at a temperature of 100F.

This vinyl chloride product contained essentially no l,2-dichloroethane. The bottoms from the vinyl chloride column at a temperature of 205F and containing about 40 weight'percent of vinyl chloride and 60 weight percent of l,2-dichloroethane was recycled to the Dichloroethane Column.

EXAMPLE I] A multi-component feed stream comprising 60 weight precent vinyl chloride, 32 weight percent hydrogen chloride and 8 weight percent l,2-dichloroethane was passed to a condenser at 300F and 200 psig. A two-phase liquid-gas stream from the condenser at 100F and 185 psig was then passed to a drum. From the drum, the gaseous phase was passed to an upper zonule and the liquid phase to a lower zonule of a distillation column divided into upper and lower zonules by an intermediate blind plate. The upper zonule was operated at 170 psig and a temperature range of 80 to -l5F; the lower zonule was operated at 200 psig and a temperature range of 120 to 170F. The gaseous phase comprising 53 weight percent vinyl chloride, 47 weight percent hydrogen chloride and 1 weight percent ,l,2-dichloroethane, was admitted below the lowest dichloroethane, was admitted above the highest plate I weight percent in the lower zonule. A liquid stream from below the lowest plate in the upper zonule comprising weight percent vinyl chloride, 14 weight percent hydrogen chloride and 1 weight percent l,2-dichloroethane was removed and recombined with the multi-component feed stream between the condenser and drum. A gaseous stream from above the highest plate in the lower zonule comprising 67 weight percent vinyl chloride, 32 weight percent hydrogen chloride and 1 weight percent l,2-dichloroethane was removed and recombined with the multi-component feed stream ahead of the condenser. Substantially pure hydrogen chloride was removed as overhead from the upper zonule. A stream comprising 84 weight percent vinyl chloride and 16 weight percent l,2-dichloroethane was removed as bottoms from the lower zonule.

EXAMPLE I A multi-component feed stream comprising 57 weight percent vinyl chloride, 32 weight percent hydrogen chloride and l 1 weight percent l,2-dichloroethane was passed to a condenser at 330F and 185 psig. A two-phase stream from the condenser at F and 180 psig was then passed to a drum. From the drum, the gaseous phase was passed to an upper zonule and the liquid phase to a lower zonule of a distillation column divided into upper and lower zonules by an intermediate zone of cooling coils cooled with cooling water. The upper zonule was operated at 175 psig and a temperature range of -l5 to 80F; the lower zonule was operated at 185 psig and a temperature range of F to F. The gaseous phase, comprising 54 weight percent vinyl chloride, 45.5 weight percent hydrogen chloride and 0.5 weight percent l,2-dichloroethane, was admitted below the lowest plate in the upper zonule; the liquid phase, comprising 77 weight percent vinyl chloride, 16 weight percent hydrogen chloride and 7 l,2-dichloroethane, was admitted above the highest plate in the lower zonule. Substantially pure hydrogen chloride was removed as overhead from the upper zonule. A stream comprising 84 weight percent vinyl chloride and 16 weight percent l,2- dichloroethane was removed as bottoms from the lower zonule.

It is to be understood that the invention is not limited by the specific examples and embodiments described hereinabove, but includes such changes and modifications as may be apparent to one skilled in the art upon reading the appended claims.

What is claimed is:

l. A method for distilling a multi-component stream having a gaseous phase and a liquid phase comprising:

A. separating the gaseous phase from the liquid phase;

B. passing the separated gaseous phase and liquid phase to a distillation column divided into a separate upper zonule and a separate lower zonule by a blind plate wherein the separated gaseous phase is passed to the upper zonule for separate distillation thereof and the separated liquid phase is passed to the lower zonule for separate distillation thereof;

C. distilling the gaseous phase and the liquid phase in their respective zonules while,

1. withdrawing from the upper zonule,

a. as a substantially pure gaseous distillate, one of the components of said gaseous phase, and b. as a liquid distillate, at least one other component of said gaseous phase other than the component in the gaseous distillate, and 2. withdrawing from the lower zonule,

a. as a liquid effluent, components of said liquid phase. and 1 b. as a gaseous effluent, at least one other component of said liquid phase other than the components in the liquid effluent; and

4. The process of claim 1 wherein the two-phase mu]- ti-component stream is formed by the partial condensation of a substantially vaporour multi-component stream and the separation of the gaseous phase from the liquid phase is achieved by passing the two phases to a knockout drum and removing therefrom the separated gaseous phase and the separated liquid phase.

5. The process of claim 4 wherein the liquid distillate and the gaseous effluent are recombined with the multi-component stream by passing the liquid distillate to the two-phase multi-component stream prior to separation of the gaseous phase and the liquid phase and by passing the gaseous effluent to the vaporous multicomponent stream prior to the partial condensation thereof.

6. The process of claim 4 wherein the liquid distillate and the gaseous effluent are recombined with the mul ti-component stream by passing the liquid distillate and the gaseous effluent to the vaporous multi-component stream prior to its partial condensation.

7. The process of claim 2 wherein the vaporous multi-component stream contains vinyl chloride, 1 ,2- dichloroethane and hydrogen chloride, the gaseous phase is rich in vinyl chloride and hydrogen chloride and contains lesser amounts of l,2-dichloroethane, the liquid phase is rich in vinyl chloride and contains lesser amounts of l,2-dichloroethane and hydrogen chloride; the liquid distillate is rich in vinyl chloride and contains lesser amounts of hydrogen chloride and 1,2- dichloroethane; the gaseous effluent is rich in vinyl chloride and contains lesser amounts of hydrogen chlo- D. recombining at least part of the liquid distillate ride and l,2-dichloroethane; the gaseous distillate is substantially pure hydrogen chloride and the liquid effluent is a substantially pure mixture of vinyl chloride and l,2-dichloroethane.

8. The process of claim 7 wherein the liquid distillate and the gaseous effluent is recombined with the multicomponent stream by passing the liquid distillate to the two-phase multi-component stream prior to separation of the gaseous phase and the liquid phase and by passing the gaseous effluent to the vaporous multicomponent stream prior to the partial condensation thereof.

9. The processv of claim 7 wherein the liquid distillate and the gaseous effluent are recombined with the multi-component stream by passing the liquid distillate and the gaseous effluent to the vaporous multi-component stream prior to its partial condensation. 

1. A METHOD FOR DISTILLING A MULTI-COMPONENT STREAM HAVING A GASEOUS PHASE AND A LIQUID PHASE COMPRISING: A. SEPARATING THE GASEOUS PHASE FROM THE LIQUID PHASE; B. PASSING THE SEPARATED GASEOUS PHASE AND LIQUID PHASE TO A DISTILLATION COLUMN DIVIDED INTO A SEPARATE UPPER ZONULE AND A SEPARATE LOWER ZONULE BY A BLIND PLATE WHEREIN THE SEPARATED GASEOUS PHASE PASSED TO THE UPPER ZONULE FOR SEPARATE DISTILLATION THEREOF AND THE SEPARATED LIQUID PHASE IS PASSED TO THE LOWER ZONULE FOR SEPARATE DISTILLATION THEREOF; C. DISTILLING THE GASEOUS PHASE AND THE LIQUID PHASE IN THEIR RESPECTIVE ZONULES WHILE,
 1. WITHDRAWING FROM THE UPPER ZONULE, A. AS A SUBSTANTIALLY PURE GASEOUS DISTILLATE, ONE OF THE COMPONENTS OF SAID GASEOUS PHASE, AND B. AS A LIQUID DISTILLATE, AT LEAST ONE OTHER COMPONENT OF SAID GASEOUS PHASE OTHER THAN THE COMPONENT IN THE GASEOUS DISTILLATE, AND
 2. WITHDRAWING FROM THE LOWER ZONULE, A. AS A LIQUID EFFLUENT, COMPONENTS OF SAID LIQUID PHASE, AND B. AS A GASEOUS EFFLUENT, AT LEAST ONE OTHER COMPONENT OF SAID LIQUID PHASE OTHER THAN THE COMPONENTS IN THE LIQUID EFFLUENT; AND D. RECOMBINING AT LEAST PART OF THE LIQUID DISTILLATE AND AT LEAST PART OF THE GASEOUS EFFLUENT WITH THE NUMULTICOMPONENT STREAM.
 2. withdrawing from the lower zonule, a. as a liquid effluent, components of said liquid phase, and b. as a gaseous effluent, at least one other component of said liquid phase other than the components in the liquid effluent; and D. recombining at least part of the liquid distillate and at least part of the gaseous effluent with the multi-component stream.
 2. The process of claim 1 wherein the two-phase multi-component stream is formed by the partial condensation of a substantially vaporous multi-component stream.
 3. The process of claim 1 wherein the separation of the gaseous phase from the liquid phase is achieved by passing the two phases to a knockout drum and removing therefrom the separated gaseous phase and the separated liquid phase.
 4. The process of claim 1 wherein the two-phase multi-component stream is formed by the partial condensation of a substantially vaporour multi-component stream and the separation of the gaseous phase from the liquid phase is achieved by passing the two phases to a knockout drum and removing therefrom the separated gaseous phase and the separated liquid phase.
 5. The process of claim 4 wherein the liquid distillate and the gaseous effluent are recombined with the multi-component stream by passing the liquid distillate to the two-phase multi-component stream prior to separation of the gaseous phase and the liquid phase and by passing the gaseous effluent to the vaporous multi-component stream prior to the partial condensation thereof.
 6. The process of claim 4 wherein the liquid distillate and the gaseous effluent are recombined with the multi-component stream by passing the liquid distillate and the gaseous effluent to the vaporous multi-component stream prior to its partial condensation.
 7. The process of claim 2 wherein the vaporous multi-component stream contains vinyl chloride, 1,2-dichloroethane and hydrogen chloride, the gaseous phase is rich in vinyl chloride and hydrogen chloride and contains lesser amounts of 1,2-dichloroethane, the liquid phase is rich in vinyl chloride and contains lesser amounts of 1,2-dichloroethane and hydrogen chloride; the liquid distillate is rich in vinyl chloride and contains lesser amounts of hydrogen chloride and 1,2-dichloroethane; the gaseous effluent is rich in vinyl chloride and contains lesser amounts of hydrogen chloride and 1,2-dichloroethane; the gaseous distillate is substantially pure hydrogen chloride and the liquid effluent is a substantially pure mixture of vinyl chloride and 1,2-dichloroethane.
 8. The process of claim 7 wherein the liquid distillate and the gaseous effluent is recombined with the multi-component stream by passing the liquid distillate to the two-phase multi-component stream prior to separation of the gaseous phase and the liquid phase and by passing the gaseous effluent to the vaporous multi-component stream prior to the partial condensation thereof.
 9. The process of claim 7 wherein the liquid distillate and the gaseous effluent are recombined with the multi-component stream by passing the liquid distillate and the gaseous effluent to the vaporous multi-component stream prior to its partial condensation. 